Extruding Sheet Metal Model on Flange

craig_townsend418

I am working on a sheet metal model, and am extruding various parts, but I have stumbled upon a problem with an extrude on a flange. I have created a variable of #Etch (thickness 0.022") that my sheet metal model uses over and over to extrude parts (thickness of #Etch = thickness of sheet metal model). Using the same method I used on the rest of the model, I created a flange, then created a new sketch on top of the flange to extrude the open parts. 

The problem becomes evident on two flanges that are at 45 degrees to the rest of the model. Creating a flange, then sketching on top, then extruding said sketch is resulting in a error message "Sheet Metal Model can not be built". I'm not sure how to fix this issue. The extrude is only the depth of the sheet metal model. This method worked just fine on the opposite 90 degree flange. 



I have attached a link to the file below.
https://cad.onshape.com/documents/ace02dca554841d82ca31887/w/dec9cbb1fc8fb227f8635678/e/04c21757a943e406a5dc300a



Another unrelated, but related question. Regeneration times seem to be slowing with every extrude I make. Any way to deduce the regeneration times?


Thanks in advance,
Craig Townsend

NeilCooke

Hi Craig - Sheet Metal is very picky about the geometry it creates and it is also very "expensive" (in terms of regeneration times) when using extrudes and should be avoided if possible. I think the best solution for this model would be to create it as a surface and convert it after. I will build an example for you later today.

NeilCooke

I hope you can follow what I have done https://cad.onshape.com/documents/57842cc8dc7b0b0db9c2eceb/w/00fb2647a8ad36a15a0c8c51/e/a00d45e9c346779007ef9d4a

craig_townsend418

Neil,
Still trying to follow what you did to learn the process, but my follow up question may lead itself to your solution. In the original drawing I had a flange with the upper half extruded away, and the bottom half visible. On the final model, I need to take that top upper half of the flange and bend it at a more acute angle which I was able to do. However, I need to create an additional flange (top view) on the angled flange. I get a collision on the sheet metal when I attempt to do that between the two flanges. Would I just need to adjust the height of the new flange so that it doesn't cover the whole length?



If this helps, this is the prototype that I'm basing this model on. The front window area is the 90 degree flange, with the 'top cover' piece being covered with a layer of snow. 



Craig 

craig_townsend418

To complicate things more, I originally linked the wrong file. This is the correct file. I forgot about the floor sheet. I started with the floor and flanged the edges off that, so the floor of the model would be a complete single piece. 


https://cad.onshape.com/documents/7a29ad8a8fc43a93ee0c7198/w/3bd0f1d1f3dfcc6c7c5a06df/e/0af508357951e63beb1d104a

Sorry for that mistake. Does that change how the flange is created & removed?
Craig 

lana

@craig_townsend418
Great project!
You can see that this model can't possibly be build from a single piece of sheetmetal.
You'll to build two pieces and weld them together. You can use bend table to convert one of the bends to rip and continue with two parts.


Use RMB menu for the bend you want to convert.

craig_townsend418

@NeilCooke @lana

So I've progressed on this model a little more and need one final flange to complete the model, but I can't seem to quite get it to join. If the flange 4 is flat (height consistent) the join flange tool works fine. However, once I introduce a slope to flange 4, I can't use the join flange function. Flange 5 needs to cover both flange 4 and the mirror of flange 4.


https://cad.onshape.com/documents/7a29ad8a8fc43a93ee0c7198/w/9fc0941b5562f76e6d549e45/e/0af508357951e63beb1d104a


I did figure out a 'trick' to extrude an edge of a flange like I've done on flange 3. By drawing a line .001" from the fold line and then extruding the model is tricked into thinking that the flange can still can built with partial flange extruded (because it 'sees' the whole flange as .001" wide at the minimum.

lana

Like this ?

craig_townsend418

@lana Yes. Can you explain how you did that?

Jake_Rosenfeld

@craig_townsend418

There is a link below the image so that you can look through all the steps Lana took to get to the final product.  Click on "Like this?"

craig_townsend418

Jake_Rosenfeld said:

@craig_townsend418

There is a link below the image so that you can look through all the steps Lana took to get to the final product.  Click on "Like this?"

I didn't see it in my original reply.

But looking at the steps, it's similar to what I was doing. Create flange, extrude, create new flange on top of extruded area, and join. I guess I'm just not understanding why I couldn't accomplish the same thing.

lana

Please notice that Flange 4 creates two patches now, this closes the gap between them. Also I've aligned Flange 5 with trimmed flange 4 and reduced its length.  However, when building a sheet metal shape of this complexity, you might do better by building a solid model first and then using sheet metal Model convert option to get all the geometry at once. That would be an easier way to match all the corners.
  

craig_townsend418

Thanks for the explanation. It helps me understand how to move forward on future models with solid models and then converting them at the end.